1. Field of the Invention
This invention relates to image cutout methods and apparatus, and more specifically to an image cutout method and apparatus for converting an image into data form for digital processing to cut out an image of a desired subject therefrom.
2. Related Art Statement
In recent years, the technology of digital image processing for converting an image into data form for digital processing has been widely used. Also in a field of a photomechanical process for making a printing plate including images, by introducing the technology of digital image processing, most works which had previously been done depending on workers' experiences and intuition were automated, and as a result it became possible to efficiently make a high quality plate even by workers without high skills.
"Cutout" is one of the processes in the photomechanical process. This is a process for cutting out a subject part from an original photographic image with a background. For example, this process is performed when a plate for a catalog or an advertising leaf let is made containing a photograph of a product. If this is done by hand, much expense in time and effort is required. Therefore, a method has been devised that the original photograph is read by a scanner to be converted in data form and the obtained image data is subjected to digital processing to be cut out.
The method is as follows, for example. That is, the image data is binarized with an appropriate reference color (for example, Y, M, C, K) and (positional information of) a boundary line where the obtained bit map is on/off is obtained. Then, only data inside the obtained boundary line is extracted. Thus, the image of the subject part can be cut out from the original image without tracing by an operator.
However, in the above method, it is possible to accurately cut out the image of the subject part when the subject (and the background) has a single-color or a color close thereto, while it is possible to obtain only part of the accurate contour line whichever color is selected for a reference color for binarization when a plurality of colors are included in the subject. For example, when a subject 1101 shaped like a human as shown in FIG. 11 is to be cut out, if the reference color is set based on a color of a body part 1101a, the accurate contour line cannot be obtained in a head part 1101b, and if the reference color is set based on a color of the head part 1101b, the accurate contour line cannot be obtained in the body part 1101a.
Thus, a new method as disclosed in Japanese Patent Publication (examined)63-5745 by the applicant has been suggested. That is, as shown in FIG. 12, the method is for setting a window frame (hereinafter referred to as a nozzle 1201) on a display screen and, with moving the nozzle 1201 along a contour of a subject, binarizing image data in the nozzle 1201. In this method, it is possible to obtain the accurate contour line of the entire subject 1101 by setting an appropriate reference color for each nozzle 1201 even when a plurality of colors are included.
By the way, in the embodiment shown in the above publication, an operator manually performs processing of moving the nozzle 1201 along the contour of the subject 1101. That is, the operator roughly traces the contour of the subject 1101, and from the approximate contour part obtained thereby, a system side traces an accurate contour line.
Specifically, in FIG. 12, the operator first moves the nozzle 1201 to a cutout starting position and sets a reference color. In response, the system side binarizes the image data in the nozzle 1201 to perform processing for obtaining a partial contour line in the nozzle 1201. Next, the operator moves the nozzle 1201 in a direction shown by an arrow in the drawing along the contour of the subject 1101, and further changes the reference color as required. In response, the system side binarizes the image data in the nozzle 1201 after movement to perform processing for obtaining a next partial contour line. Thereafter, the operator and the system repeat the above operation and processing to obtain contour lines of the subject 1101 and the background.
In the above new method, if the processing of moving the nozzle 1201 along the contour of the subject 1101 is performed by the system side, it is possible to further reduce a load on the operator thus perform prepress more efficiently. However, in the above publication and any other publications, processing of automatically moving the nozzle 1201 is not disclosed.
This may be because it is not easy to automatically move the nozzle 1201 on the grounds as follows. That is, the operator can intuitively distinguish the subject 1101 from the background when looking at the photographic image shown in FIG. 12. However, the system side cannot distinguish which data belongs to the part of the subject 1101 and to the background part among the held image data. Thus, moving the nozzle 1201 along the contour of the subject 1101 is easy for the operator, but not for the system side because the system cannot recognize the contour.